Environmental concern has spurred interest in recycling many materials of manufacture. This recycling serves many useful purposes. One, it helps to conserve natural resources. Two, it also provides a way to productively deal with the huge quantity of waste generated today.
Well-known recycling programs include reclaiming paper from used newspapers and aluminum from used beer and soft drink cans.
Polyethylene teraphthalate (PET) has been widely used in the soft drink industry as a material for making soda bottles. Due to the popularity of using PET to manufacture soft drink bottles, there is already a large volume of PET bottle scrap available. Furthermore, the amount is expected to increase each year, especially as more states join those states that have already passed laws requiring a deposit on PET bottles so as to encourage their return.
However, there are difficulties with reclaiming PET scrap from used PET bottles. Often, the bottles have been ground to flake, which contains not only PET, but also may contain such contaminants as paper, polyethylene, ethylvinyl acetate from glue, paint, and aluminum from bottle caps. Many methods for removing these contaminants exist. For example, the paper can be removed by an air-fluidized bed and the polyethylene can be removed by a flotation process using water. As for the aluminum, one known method for its removal utilizes hydrocyclone separators. The aluminum content of the scrap can only be reduced by such a process to about 0.05% by weight of the scrap. Moreover, in order to accomplish this, about 50% of the PET flake is lost. Such a yield makes PET flake reclaimed from bottle scrap more expensive than virgin "2GT" flake.
The present invention provides for a different method of removing aluminum from PET bottle scrap.